Tv Tuners

Did a job today in a location where readings fluctuated all over the roof- countryside reflected signal, no electric fences. Spectrum showing modulation across the top on most channels. Typical MER 22, PreBer E-3, post BER E-6, NM 1-3 db, Ch level around 58db. I've had success with worse. Anyway, run one temp cable through window and got the TEAC LCD ( built in DVD) tuned. Plenty of pixellation. Got out a test STB (Phoenix) and showed customer perfect channels holding up all round. BER readings on STB showing no errrors.

Told him to take back the TV ( new out of box today) and get a Panasonic. His mate at Harv Norman said all the tuners are the same so he's looking for an arguement. AFAIK there are about four tuner manufacturers- guessing Thomson, Phillips, Samsung and ...? Can anyone shed light on this? I assume that not only the tuner but the firmware running the COFDM process through the tuner sets the TV's ability to maintain a solid picture.

First off ,guessing being rural that there are probably no strong signals around E.G analog TV,FM radio ,Phone towers etc as these can cause issues with a "lesser" quality tuner but can be filtered out if the problem.But definitely must be checked before blaming Tuner.

Bad tuners have always been a problem.

Even in analog days you would get the odd one that had a snowy pic or herringbone patterns or bad ringing but these were one offs rather than model related.( until the Chinese crap hit the market circa 2000 and POOR TUNERS proliferated)

With Digital you still get the odd one that leaves the factory that doesn't work as it should .Generally these are also one offs .

There have been several STBs that did perform "on average" more poorly than other brands particularly on less than ideal signals .DGtec and Wintel come to mind .

There have been some models of TV with Digital tuners that were unable to handle fluctuations in signals as would happen when wind blows trees in path.Some Sonys and LG models as I recall .

As an installer when faced with one of these "dogs" we have to decide when its no longer our problem.

I guess I feel for the customer as The usual scenario is that TV is returned to the service center where it is tested for a short period of time and in almost every case is returned as" no fault found".They are stuck with a lemon and we have to try to make it work.

Often faulty tuners only start to play up once the Sets warmed up or only when its cold.The temperature of the service center or the amount of soak test time will have a bearing on whether the fault shows up or not.

Often the service center is in a different area and isn't on the same channels so the fault doesn't appear possibly due to different characteristics of the tuner at different frequencies. ( obviously re-tuned to test)

The signal levels at the service center will usually be different from what you had at the customers house. Sometimes much weaker sometimes much stronger.Again these variations may or may not show up the fault condition experienced at customers home.

Things I've used to trick a "dog"

1) Fit a FL3BPMH filter to knock out any out of band crap

2) Fit a variable attenuator and fixed ones to see if it will play the game with very low signals .

3) Fit a small distribution amp say around 12-16dB to see if more signal helps.

4) If its a UHF adjacent analog channel issue ,carefully notching it out with a Laceys SF4/SF5 can fix.( If antenna position can't reduce it)

5) I'm tired and forgotten but there was another

6) Sell them a STB that works

When assisting customers with potential warranty claims ,write down all the digital readings for each channel E.G

Write down all analog TV channel readings This will rule out any onsite overload issues
Write down highest levels of FM radio channels. Ditto

Write down any things such as reducing levels below /increasing levels above to help or that several other STBs tried worked OK

It also helps to note AS standards levels to show that what you have is in the bounds of expected performance .

If nothing else it may help to convince the service tech that an antenna tech has been to customers place and confirmed that the TV is not working on a signal that is concidered OK and convince them to look a little further.

Thanks Bellotv. The customer was recommended by his pal who works for HV to get the TEAC because it has the DVD player inbuilt. I told him to just replace the TEAC with a Pana and get a separate DVD player- after all to play a DVD on the TEAC still requires the 'Source' button to be pressed and scrolled down to DVD rather than AV. I think the swap over will not be a problem. I told the customer that once the PAna is going I can then address any issues with pic quality. I don't expect there to be any unless it's very windy. BTW, Your neck of the woods is similar to the Huon Valley- plenty of bush, rolling hills and valleys tucked away. Bit warmer though!. Cheers.

His mate at Harv Norman said all the tuners are the same so he's looking for an arguement. AFAIK there are about four tuner manufacturers- guessing Thomson, Phillips, Samsung and ...? Can anyone shed light on this? I assume that not only the tuner but the firmware running the COFDM process through the tuner sets the TV's ability to maintain a solid picture.

Yeah, it could be noise figure of the tuners playing a part as well. A while ago I struck a bunch of small screen TV's that required >50dB's to give a stable picture.

post viterbi BER 1x10^6 is considered Quasi error free. Sure not ideal, but if a tuner is severely pixelating at 58db with Pv 1x10^6 then I'd be suspecting a faulty tuner.

I said pBER of E-6 was typical, not quite true- more of an average across the range. One channel would show preBER E-5, pBER E-8, NM +20 then for would drop to pre of E-2 and post E-4, NM -3db, didn't have enough time to get it more consistent. Point is the crappy tuner couldn't handle it- even channels with solid readings were pixellating, as you say the tuner could be faulty.